Electric heater



June 12, 1956 1.. P. HYNES ELECTRIC HEATER 4 Sheets-Sheet 1 Filed Aug.12, 1952 INVENTOR ATTORNEYS.

June 12, 1956 L. P. HYNES ELECTRIC HEATER Filed Aug. 12, 1952 4Sheets-Sheet 3 INVENTOR L ee H yn ea ATTORNEYS.

June 12, 1956 P. HYNES ELECTRIC HEATER 4 Sheets-Sheet 4 Filed Aug. 12,1952 2375,47 Patented June 12, 1956 w ll ELECTRIC HEATER Lee I. Hynes,Haddoniield, N. 3., assignor to Turbine Equipment Company, New York, N.Y., a corporation at New lei-soy Application August 12, 1952, Serial No.303,949

12 Claims. (Cl. 219-49) The present invention relates to electricheaters, particularly of the type which are used to heat conduits andthe like.

A purpose or" the invention is to reduce the overall size of electricheaters for conduits and the like and simplify the construction.

A further purpose is to reduce the cost and increase the reliability ofattachment for interconnection between a metallic heater strap and aheater insulator along the strap.

A further purpose is to reduce the rejections on insulators for electricheaters by making them moldable by flow entirely in one direction,avoiding the necessity for lateral flow under molding.

A further purpose is to make electric heaters for conduits moreaccessible.

A further purpose is to enable the supplier to ship the heater pipe tothe field and assemble the electric heater in the field.

A further purpose is to provide more eifectively for expansion andcontraction of electric heater pipes and of electric heaters.

A further purpose is to make electric heater constructionexplosion-proof.

A further purpose is to provide clips at intervals along a metallicstrap of an electric heater and to engage the clips into clip sockets atopposite ends of the insulators near the side of the insulatorsadjoining the strap so as to secure the insulators to the strap.

A further purpose is to lance the clips from the strap.

A further purpose is to mount both electric resistors and terminals inaligned longitudinal holes throughthe insulators.

A further purpose is to make provision in the insulators alternativelyto receive circular resistors and strip resistors.

A further purpose is to secure the metallic straps at intervals toheater bars and to lance clips from the straps to engage in clip socketsat opposite ends of the resistors.

A further purpose is to provide anti-friction bearings suitably in theform of rollers, balls or ball circumference portions on the straps toengage the inside of the heater pipe during longitudinal motion of thestrap or heater pipe.

A further purpose is to extend both ends of the heater pipe through thewall of the conduit and desirably provide stufling boxes to engage andseal the pipe as it passes through the conduit, thus permitting accessto both ends or" the heater outside the conduit.

A further purpose is to extend the heater pipe in a gradual curve andcarry it out through the wall of the conduit at at least one end so thataccess to the heater can be obtained beyond the conduit.

A further purpose is to provide radially extending sliding elements onthe heater pipe to space the heater pipe from the conduit and slidealong the conduit.

A further purpose is to provide a frame inside an insulated casing tosupport outgoing and incoming conduits r'rs! and also to support theheater pipe in expansible and contractable relation.

Further purposes appear in the specification and in the claims.

In the drawings I have chosen to illustrate a few only of the numerousembodiments in which my invention may appear, selecting the forms shownfrom the standpoints of convenience in illustration, satisfactoryoperation, and clear demonstration of the principles involved.

Figure 1 is a side elevation partly broken of a heater minus the heaterpipe as used in the invention.

Figure 2 is a front elevation of a desirable embodiment of insulator.

Figure 3 is a central longitudinal section of the insulator of Figure 2,showing the interconnection between the metallic strap and theinsulator.

Figure 4 is a fragmentary side elevation of the strap and insulator atthe terminals.

Figure 5 is a transverse section of a variant embodiment of the heaterof the invention, omitting the resistors.

Figure 6 is a fragmentary side elevation of the embodiment of Figure 5showing one terminal and resistor arrangement.

Figure 7 is a variant of Figure 6 showing another terminal arrangement.

Figure 8 is a fragmentary side elevation of the electric heater ofFigure 5 omitting the heater pipe and omitting the resistor elements.

Figure 9 is a transverse section similar to Figure 5 showing a variantin the electric heater of the invention, omitting the resistors.

Figure 10 is a fragmentary longitudinal section of the heater of Figure9, on the line 10-10, including the resistors.

Figure 11 is a fragmentary top plan view of the strap and clips used inFigures 9 and 10, omitting other structure.

Figure 12 is a reduced scale transverse section of a variant form ofheater of the invention omitting the resistors.

Figure 13 is a side elevation of the form of Figure 12 partly in centrallongitudinal section and omitting the pipe and resistors.

Figure 14 is a transverse section of a variant heater in accordance withthe invention omitting the resistors.

Figures 15 and 16 are fragmentary detail side elevations, partly incentral longitudinal section in Figure 16, showing variant bearingsapplied to the metallic strap.

Figure 17 is a fragmentary transverse section of the heater pipe andstrap showing a still further variant of the bearing.

'Figure 18 is a fragmentary longitudinal section of a conduit and heaterin accordance with the invention showing the installation of the heaterin the conduit.

Figure 19 is a fragmentary longitudinal section of a conduit and heatersof variant construction.

Figure 20 is an enlarged transverse section through a conduit and heaterof Figures 18 and 19 omitting the in terior construction of the heater.

Figure 21 is a fragmentary central longitudinal exploded section showingthe endwise joining of heater pipes inside the conduit.

Figure 22 is a fragmentary side elevation of a heater of the invention,showing the terminal construction.

Figure 23 is a fragmentary side elevation showing the joining endwise oftwo heater assemblies inside the heater pipe.

Figure 24 is an enlarged section of Figure 23 on the line 2424.

Figures 25, 26 and 27 are circuit diagrams showing variant forms ofheater connections in accordance with the invention.

Figure 28 is a fragmentary enlarged side elevation of the terminalconstruction in accordance with the invention.

Figure 29 is an axial section further enlarged showing the connection ofa cable to the structure of Figure 28.

Figure 30 is a transverse section through a conduit and heater tubeshowing a variant form of the invention.

Figure 31 is a fragmentary side elevation of a modified form of heaterpipe in accordance with the invention.

In the drawings like numerals refer to like parts throughout.

Describing in illustration but not in limitation and referring to thedrawings:

Electric heaters for conduits and the like as shown in my U. S. PatentNo. 1,997,146, granted April 9, 1935, for Electric Heater have beenextensively used for thawing ice around gates of power plants and thelike, and for preventing freezing and maintaining proper viscosity inlines through which water, oil, tar, chemicals and the like are causedto fiow. In the construction of my prior patent, it was necessary toemploy a complicated and expensive insulator, which underwent flow intwo different directions during molding, and was correspondingly subject to a high cost and high rejection rate. The attachment of theinsulator to the strap was acomplished by cotter pins, and necessitatedthat holes for this purpose run clear through the insulator in adirection transverse to the length of the insulator.

Because of the complexity of the construction, it was usually necessaryin the prior art to install the complete heater prior to shipment, andthe construction did not lend itself as well as the present constructionto field assembly.

It was often difficult in the prior constructions used to obtain accessto the heater and rarely in the prior constructions were both ends ofthe heater accessible. The tendency more recently has been to increasethe size of installations, often running heated conduits for severalhundred feet between terminal points. i

In accordance with the present invention, the construction of theinsulator has been greatly simplified, the cost of production has beenreduced, and the manner of the attachment of the insulator to themetallic strap has been improved. Field installation is now very readilyaccomplished. Improved arrangements are made for access to one or bothends of the heater even though the conduit may be in a duct or actuallyburied beneath the ground.

The improved construction lends itself very well to terminalarrangements, and the same insulators can be used to support theterminals as those employed to support the resistor. The insulators mayalso interchangeably support round or strip resistors.

Improved provision has also been made for longitudinal motion of theelectric heater inside the heater pipe, whether due to expansion andcontraction or otherwise, and also for longitudinal expansion andcontraction of the heater pipe itself.

The improved construction lends itself well to use around inflammablefluids, and where desired may be made explosion-proof.

Figure 1 shows an electric heater having an elongated metallic strap 4%)reversely bent at one end 41 so as to engage an anchor and suitablycurved at the other end 42 to protect the endmost insulator and crossconnection against the end of the surrounding pipe. As in all of theforms of the invention, resistors 43 run longitudinally through openingsin a line of insulators 44 which are secured to the strap 40 in a mannerwhich will be described. The resistors are connected at one end to aterminal block 45 and at the other end are suitably cross connected at46. The form of Figure 1 will serve as a generic showing of the generalconstruction, in order to simplify the showing of the remaining formsand avoid Cir , lators and will receive a large number of resistors.

i the necessity of repeating the resistors and other features common toall of the forms.

The preferred embodiment of the insulator is shown in Figures 2, 3 and4, consisting of an insulator block 47 of suitable refractory such asporcelain having a plurality of longitudinally extending openings 48which are in line throughout the group of insulators and receive theresistors 43 already described. In the form shown the openings 48 areround, but have suitably hexagonal bolt head sockets St) at one end foruse on terminals.

The particular insulator block shown has a pentagonal outer rim 51, butit will be understood that any desired form whether circular orpolygonal may be used. The insulator has opposite ends 52 which areprovided, adjoining one side which is to engage the metallic strip 40,with opposed clip sockets 53. The preferred form as shown has oppositelydiagonal engaging surfaces 54 of the clip sockets to receive the clips.In this form the metallic strap 40 has clips 55 lanced from the stripsin pairs and deformed by bending into the clip sockets so as to engagethe insulator and hold it effectively in place against the strap 46.

At the terminal the resistors 43 are engaged by terminal bolts 56 whichextend through the openings 43 and carry the usual nuts to engageterminal wires 57 which extend to connecting wiring.

The insulators and strap of Figures 2 to 4 along with the resistorsextending through the openings of the insulators are surrounded by aheater pipe not shown in Figures l to 4, but illustrated at 58 in Figure5. In the form as shown in Figures 5 to 8 inclusive, the insulator block60 is of octagonal form and has opposed clip sockets 53 as alreadydescribed. The openings 48 which extend longitudinally through theinsulators and are in line throughout the group of insulators are inthis case of keyhole form, with a round portion in the center adapted toreceive a helical resistor 43 as shown in Figure 6 and with slots 61 atopposite positions on the round portion extending longitudinallythroughout the insulator and adapted to receive a strip resistor 43 asshown in Figure 7. Where the helical or other round resistor is used, Imay nevertheless employ a strip metallic terminal 62 engaged in theslots 61 of the endmost insulator and having terminal screws 63 and 64,one engaging the resistor and the other engaging the lead. Where thereis a strip or ribbon type of resistor the resistor may extend clear tothe end and be provided with a terminal screw 64 as shown in Figure 7 toengage the lead.

The means of attachment of the insulators is somewhat ditferent in theform of Figures 5 to 8. In this case a comparatively light strap 40having the clips 55 lanced from it as in the form of Figures 2 to 4 ismounted on a relatively heavier heater bar 65 by bolts 66 at intervals.and conveniently located for accessibility at points at which the clipsof a pair diverge.

In the form of Figures 9 to 11 the strap and clip construction variesslightly in that the clips 55' are suitably of separate metallic stockspot welded to the metallic strap 40 as at 67 (Figure 11). The clipsockets 53 in the insulators are effectively the same but in this casethe insulators 68 are generally cylindrical with flats 70 to engage thestraps. Spacer ribs 71 are placed around the circumference of theinsulators to protect the insulators against the pipe and permit a lowfrictional engagement between the insulators and the heater pipe.

In Figures 12 and 13 a different insulator block 72 is shown which ismore truly cylindrical with a flat 70' Where it engages the strap.

The form of Figures 12 and 13 has a large number of holes 48 which arein line throughout the different insu- In normal operation of the heaterthere is a considerable amount of expansion and contraction as theheater heats and cools and as the medium changes its temperature aroundthe heater pipe. It is therefore very desirable to facilitatelongitudinal movement of the metallic strap with respect to the heaterpipe not only from the standpoint of expansion and contraction but alsoto permit insertion and removal of long lengths of heater elementsinside the heater pipe.

In Figure 14 the strip 40 is provided with journals 73 united to thesides as by welding and providing bearings for roller bearings 74 (seealso Figure Another form of bearing construction uses a ball atintervals under the strap 40 as shown in Figure 16, where a ball socket'75 is united to the bottom of. the strap as by spot welding and retainsa freely moving ball bearing 76 which rides the inside of the heaterpipe.

In some cases it i sufiicient to have a surface engaging the pipe whichis a portion of a sphere, and in Figure 17 a hemispherical bearingslider 76' has been formed from the strip 40 at intervals to engage thepipe.

It is very desirable not only to provide for expansion of the heaterelement within the heater pipe, but also to provide for expansion of theheater pipe itself. This can often be done (Figure 18) by bending aconduit 77 containing a medium to be heated at intervals along itslength as shown at 78 and extending a heater pipe 58 out through thewall of the conduit at opposite ends as shown at 80. This has beenaccomplished by placing enlarged sleeves 31 welded into the conduit andsurrounding the heater pipe as it is carried out of the conduit, andfitting packing glands and packing 82 on the sleeves to engage theheater pipe, thus permitting relative sliding of the heater pipe. Thusthe heater pipe is accessible at one end by a terminal fitting S3 and atthe other end suitably by a cap 84 so that access can be obtained toeither end of the heater. The conduit 77 is desirably insulated by aninsulating layer 85 inside a metallic casing 86.

In some cases the conduit passes underground or in ducts for aconsiderable distance without bends, and ac cess to the heater insidethe heater pipe may be more difiicult. In this case with a relativelystraight conduit 77' I bend the heater pipe along gradual bends 87 andpass it through an opening in the conduit and weld it to the conduit,gaining access to the terminals at the ends outside the conduit (Figure19). Ends of adjoining heaters having terminals 83 are desirably broughtup together, either above the ground, or in a box or manhole. An

insulating layer 85 desirably surrounds the conduit and the conduit maybe supported on seats 88 from piers 90. The remote end of the heaterpipe in this form is closed by welding at 89.

When the heater pipe is carried for a considerable dis tance through theinterior of the conduit it is desirable to provide radial sliding andsupporting elements 91, suitably welded to the heater pipe, extendingout from the pipe and engaging the interior of the conduit as shown inFigure 20.

In some cases the heater pipe extends for such a length inside theconduit that a longitudinal joint must be made. In Figure 21 I show asleeve joint in which two sections of heater pipe are abutted within asleeve 92 which has previously been welded to one section at 93 andafter the joint is made is similarly welded to the other section.

Figure 22 shows a terminal construction which may be conveniently used.The end having the reverse bend on the metallic strap at 41 leads intothe terminal 83 which may conveniently be contained within a T having anend plug 94 and a side connection to electrical cable 95.

When two electric heater elements must be joined end to end inside theheater pipe it is desirable to use the construction of Figures 23 and24. Terminal blocks 45 are provided and from these terminal blocks leads96 extend through insulating tubes 97 which are surrounded and protectedby a suitably metallic band 98 secured by bolts 1% at a point ofoverlapping of the metallic straps so, one strap being deformed slightlyat 101. The bolts 100 serve also to unite the straps.

Any well recognized form of electrical connection may be used. Forexample Figure 25 shows resistors 43 cross connected for a three phasestar arrangement. Figure 26 shows resistors 43 connected in parallel toa single phase power source. Figure 27 shows one set of connections fora two phase circuit or two single phase circuits.

One desirable form of terminal arrangement is shown in Figures 28 and29. In this form a cable grip is mounted in the terminal T by insertingnipple 102 in the side of the T, and threading cap 103 011 the nipple atthe end remote from the T. The cap has a reduced threaded opening 104which may make threaded engagement with electrical conduit, but in theform shown receives a threaded grommet 105 and passes electrical cable95 which extends through a cable grip 107 which is threaded into a gripsocket 108 secured on the inside of the nipple in spaced relation to thenipple wall. The grip 107 has a locking collar 110 to secure the cableas well known, forming a watertight joint. The conductors in the cableare interconnected with leads 57 to the resistors by connectors 111which are suitably insulated in a manner not shown. This construction ismoisture proof and explosion proof.

In some cases it is desirable to carry several conduits 77 and 77through a duct 112 having insulation 85 and an insulating housing 86around the duct. The heater pipe and heater therein in this case iscarried through the duct 112 but outside of the conduit. Suitable spacedrelations between the outgoing conduit 77, the return conduit 77' andthe heater pipe are maintained by frames 113 located at intervals alongthe length of the duct and having elements which engage and support theheater pipe 58 and the conduits 77 and '77 and which engage the insideof the duct 112 and support the interior structure away from the conduitwall.

In some cases it is desirable to improve the heat transfer from theheater pipes to the surrounding medium especially when air and othergases are flowing through the conduit around the heater. In Figure 31 Iprovide fins 114 on the heater pipe for improvement of heat transfer inthe surrounding medium.

It will be evident that while the invention finds wide application inthe melting of ice and the heating of oil, tar and other chemicals, itmay be employed wherever elongated heaters are to be used, especiallyfor pipes and structural members of considerable length.

In view of my invention and disclosure variations and modifications tomeet individual whim or particular need will doubtless become evident toothers skilled in the art, to obtain all or part of the benefits of myinvention without copying the structure shown, and I therefore claim allsuch insofar as they fall within the reasonable spirit and scope of myclaims.

Having thus described my invention, what I claim as new and desire tosecure by Letters Patent is:

1. In an electric heater, an elongated metallic strap, clips atintervals along the strap in pairs extending diagonally oppositely fromthe strap at the same side at various points along the strap, insulatorsarranged in line against that side of the strap and having in theopposite end surfaces of the insulators opposed recesses adjoining thestrap which have opposite diagonally disposed surfaces engaged by theclips, there being at least one longitudinal opening through eachinsulator, the openings being in line throughout the group ofinsulators, and electric resistor means extending through the openingsof a plurality of the insulators.

2. An electric heater according to claim 1, in combination with aprotective pipe surrounding the strap, the insulators and the electricresistor means, and bearing means on the strap engaging the interior ofthe pipe and guiding the strap along the pipe.

3. An electric heater according to claim 1, in which the clips areintegral with and lanced from the strap.

4. An electric heater according to claim 1, in combination with electricterminals extending through and respectively mounted in an opening in atleast one of the insulators and connected to the electric resistormeans.

5. An electric heater according to claim 1, in combination with ametallic heater bar extending longitudinally, and means securing thestrap at intervals along one side of the heater bar, the clips extendingout on the side of the strap remote from the heater bar.

6, An electric heater according to claim 1, in which each of theopenings through the insulators includes a round opening and opposedslots on the opposed edges of the round opening, the round openingsbeing adapted to receive circular electric resistor means and the slotsand the round openings being adapted to receive rectangular electricresistor means.

7. An electric heater according to claim 1, in combination with aconduit for fluids, a pipe extending through the conduit and extendingbeyond the conduit at both ends, the pipe surrounding the strap,insulators and electric resistor means, packing gland means in theconduit scaling to the pipe as it leaves the conduit at each end andremovable closures for the ends of the pipe beyond the conduit.

8. An electric heater according to claim 1, in combination With aconduit for fluids, a pipe extending through the conduit, bent in acurve beyond the conduit wall, the strap, insulators and electricresistor means extending through the interior of the pipe and aremovable closure for the end of the pipe beyond the conduit.

9. An electric heater according to claim 8, in combination with radialspacers extending from the pipe and engaging the interior of the conduitin slidable relation.

10. An electric heater according to claim 1, in combination with aninsulated duct having a hollow interior, outgoing and return pipes forfluid in the duct, an electric heater pipe in the duct at one endextending through the duct wall, sealed in the duct wall and surroundingthe strap, insulators and electric heater means, and a frame engagingthe inside of the duct and engaging the outgoing and return pipes andthe heater pipe at intervals and holding the same in spaced relationwithin the duct.

11 An electric insulator comprising a ceramic block having generallycircumferential side Walls adapted to conform to the interior of a pipe,there being a flat surface at one position on the side walls, havinggenerally flat parallel end walls, there being a plurality of parallelopenings extending from one end wall to the other transverse to the endwalls and displaced from one another both laterally and transversely soas to hold a group of resistors in insulated relation, there being inthe two opposite end walls adjoining the fiat surface of the side walland symmetrically placed with respect to the longitudinal openingopposed retaining clip receiving recesses, each of the recesses having awall which is nearest to the fiat surface and which extends diagonal tothe longitudinal axis of the insulator.

12. In an electric heater terminal, a T fitting having internal threads,a nipple having male threads at the oppositc ends and threaded into thetransverse position on the T fitting, a spacer welded in the end of thenipple remote from the T fitting, an internally threaded cable gripsocket secured to the spacer inside the nipple, a cap having a femalethread at one end interthreaded with the nipple and having a reducedinternally threaded opening at the end remote from the nipple, a cableextending through the reduced opening and through the cable grip socket,a cable grip threaded into the cable grip socket and gripping the cableinside the cap, a bushing threaded into the reduced opening andsurrounding the cable, and a distribution connector interconnected withthe cable inside the nipple.

References Cited in the file of this patent UNITED STATES PATENTS1,154,416 Kuhn Sept. 21, 1915 1,273,313 Beatty July 23, 1918 1,851,939Williams Mar. 29, 1932 1,916,038 Cartwright June 27, 1933 1,963,328Holinger June 19, 1934 1,970,295 Fitzpatrick Aug. 14, 1934 1,982,885Stupakoff Dec. 4, 1934 1,997,146 Hynes Apr. 9, 1935 2,075,686 WiegandMar. 30, 1937 2,195,630 Papp et al. Apr. 2, 1940 2,288,821 Matchett July7, 1942 2,302,839 Burgett Nov. 24, 1942 2,548,360 Germain Apr. 10, 19512,598,162 Guiot May 27, 1952 FOREIGN PATENTS 71,265 Sweden Mar. 3, 1931621,411 Great Britain Apr. 8, 1949

